The present invention relates to bar codes. More specifically, the present invention is concerned with the use of bar codes for measurement.
Bar codes are widely used for identifying and tracking objects. Their applications are numerous, including sorting and inventory management.
A bar code symbol typically includes a sequence of consecutive parallel bars and spaces of varying widths that are either printed directly onto the object or printed onto labels that are affixed to the object. The bar codes are generally read by a scanning light source, such as a laser, often in the form of a handheld device. The beam of light projected onto the bar code produces a spot that is moved by an oscillating motor to produce a line or a series of lines across the bars and spaces. A sensor detects the light reflected form the bar code and converts it into an electric signal to be interpreted (or decoded) by an electronic circuit or software.
Bar codes may have different structures, each requiring a different set of rules and definitions to be interpreted. Examples of such a structure include Universal Product Code (UPC), Code 39, Codabar, and Interleaved 2 of 5. For concision purposes, the xe2x80x9cInterleaved 2 of 5xe2x80x9d bar code structure will be referred to herein simply as xe2x80x9cInterleavedxe2x80x9d
The structure of an Interleaved bar code 10 is illustrated in FIG. 1. xe2x80x9cInterleavedxe2x80x9d is a numbers-only bar code system that can only handle numbers having a even number of digits. This bar code system is said to be interleaved, because a first digit is encoded in the bars 12, and a second digit is encoded in the spaces 14. There are five bars 12, two of which 12xe2x80x2 are wide and five spaces 14, two of which 14xe2x80x2 are also wide. The interleaved 2 of 5 system allows the representation of numbers having an infinite number of digits, provided that there is a surface large enough to hold the symbols.
In the case of FIG. 1, the number 96 is provided as an example. The first digit 9 is represented by the bars 12, and the second digit 6 is represented by the spaces 14.
Bar codes, according to the xe2x80x9cInterleavedxe2x80x9d encoding system, include start and stop characters 16 and 18 as explained hereinbelow.
The use of the xe2x80x9cInterleavedxe2x80x9d structure is advantageous in many applications since it allows holding up to 18 digits per inch when printed using a 0.19 mm X dimension. As is well known in the art, the X-dimension is the width of the smallest element in a bar code symbol.
It is to be noted that, in the case of xe2x80x9cInterleavedxe2x80x9d symbols, the use of check digit is optional.
Since bar codes, in general, and the xe2x80x9cInterleaved 2 of 5xe2x80x9d system in particular, are believed to be well known in the art, they will not be described herein in further detail.
Most recent developments in bar code technology have aimed to increase the quantity and diversity of data supported by bar code symbols. However, new possibilities made possible by these new technologies remain in the context of sorting and inventory management.
Recently, a new application for bar code symbols has been in use as a measurement tool. Indeed, by aligning bar code symbols along an axis, and by predetermining positions corresponding to each bar code symbol, the scanning of a symbol may readily allow the retrieval of the coordinates of this position along the axis.
Turning now to FIG. 2 of the appended drawings, a bar code ribbon 20, according to the prior art, will now be described.
The bar code ribbon 20 comprises a plurality of bar code symbols 22 positioned in a column along the axis 24. Although the example of FIG. 2 is illustrated with symbols representing numbers using the xe2x80x9cInterleaved 2 of 5xe2x80x9d encoding system, other bar code systems can also be used. The numbers represented by each bar code symbol 22 have been provided in FIG. 2 to the left of each symbol 22.
To use the ribbon 20 for measuring positions on an object (not shown), a calibration of the ribbon 20 is first carried out. The calibration consists of measuring the distance from one end 26 of the ribbon 20 to each bar code symbol 20, and by associating this distance to a corresponding symbol 20.
In operation, by correctly positioning the bar code ribbon 20 on or near an object (not shown), positions on this object along the axis 24 may be readily determined using a conventional bar code scanner and an appropriate apparatus for decoding the symbols 20.
Of course, the ribbon 20 has to be adequately positioned on or near the object and the height of the bar code symbols should be small enough to provide the precision required by the application. The ribbon 20 can then be seen as a ruler.
Although bar code symbols encoded by other systems may be used, the use of the xe2x80x9cInterleaved 2 of 5xe2x80x9d is advantageous, since it allows for the use of smaller bar code symbols when required by the application.
A major drawback in the use of a column of adjacent bar code symbols to measure the position on an object is that the smaller the height of the symbol is, the less the orientation of the bar code scanning beam has to deviate from the horizontal to cause an incorrect reading.
FIGS. 3 and 4 illustrate how an oblique scanning beam may cause an incorrect reading of a bar code symbol when there is at least one other bar code symbol adjacent to the one being scanned.
In FIG. 3, it is shown that a beam scanning between the symbols representing the numbers 09 and 19 on the ribbon 20 along the direction represented by line 28 may incorrectly yield the decoded number 49.
In FIG. 4, it is shown that a beam scanning between the symbols representing the numbers 09 and 19 on the ribbon 20 along a direction opposite to the direction of line 28 in FIG. 3, as represented by line 30, may in this case incorrectly yield the decoded number 89. It is to be noted that, in some applications, the positions of the symbols representing the numbers 49 and 89 may be far enough from the actual scanning position to cause significant detrimental results.
A proposed solution to this problem is to use check digits on the symbols along with the encoded values. The use of check digits allows detection of incorrect readings resulting from a bad scan. However, a drawback of this solution is that it requires larger symbols, which, in some applications, may not be possible.
Of course, as illustrated in FIG. 2, the sequence of symbols may also be chosen so as to minimize the possibility or the impact of an incorrect reading, but, again, this may not be possible in some applications.
Another solution would be to provide the scanner with a means to ensure an adequate positioning relative to the symbols to scan. However, this would require either modifications to existing scanning technologies or scanning processes, which would not be universal, or a scanning method so complicated that it would cancel most of the advantages of the existing bar code scanning technology.
More specifically, in accordance with the present invention, there is provided a bar code arrangement for identifying positions along an axis, the arrangement comprising: a plurality of bar code symbols, each having start and stop end characters and encoded data therebetween; each symbol being positioned in a column along the axis and being so oriented that each bar of the symbols is parallel to the axis and that two consecutive bar code symbols have different orientations, one being rotated 180xc2x0 relative to the other; whereby a particular position along the axis may be identified by scanning the bar code symbol corresponding to the particular position among the plurality of bar code symbols in the column; a symbol scan being considered successful when two different characters are found in the symbol scan.
According to second aspect of the invention, there is provided a bar code ribbon for identifying positions along an object, the ribbon comprising: two generally parallel longitudinal sides extending along an axis; two opposite faces, each spanning between the two longitudinal sides; one of the two opposite faces having a plurality of bar code symbols printed thereon, each having start and stop end characters and encoded data therebetween; the plurality of bar code symbols being positioned on top of each other and being so oriented that their bars are parallel to the axis, and that no two consecutive bar code symbols have corresponding end characters on the same side; whereby a particular position along the ribbon may be identified by scanning the bar code symbol corresponding to the particular position among the plurality of bar code symbols in the column; a symbol scan being considered successful when two different characters are decoded following the symbol scan.
According to a third aspect of the invention, there is provided a bar-inventory management system comprising: a computer server including instructions for managing an inventory; a plurality of bar code ribbon according to the present invention to be affixed to liquor bottles; and at least one bar code scanner connected to the computer, and being configured so as to read the bar code symbols on the bar code ribbons.
According to a fourth aspect of the invention, there is provided method for identifying positions along an axis on an object, the method comprising: providing a unique bar code symbol at predetermined positions along the axis; each bar code symbol having start and stop end characters and encoded data therebetween; each bar code symbol being positioned in a column along the axis and being so oriented that each bar of the symbols is parallel to the axis and that two consecutive bar code symbols have different orientations, one being rotated 180xc2x0 relative to the other; associating in a computer database each the unique bar code symbol to a corresponding one of the predetermined positions along the axis; scanning a position along the axis until a bar code symbol having two different end characters is found; and searching in the computer database the position associated to the last scanned position.
Other objects, advantages and features of the present invention will become more apparent upon reading the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.